In recent years, the prevalence of obesity has greatly increased due to the Westernization of eating habits and the lack of activity. Obesity causes hypertension, diabetes, cardiovascular diseases and various cancers, and for this reason, interest in the prevention and treatment of obesity has increased in the world.
Although obesity itself increases the body weight, makes the body obese, and thus makes life inconvenient, the bigger problem is that obesity increases blood lipid levels to cause arteriosclerosis and heart disease, increases insulin resistance to cause complications such as diabetes, menstrual irregularity and cancer, and causes chronic adult diseases such as hyperlipidemia, hypertension, coronary artery disease and stroke. For this reason, the treatment and prevention of obesity are essential (Lee J H, J. Kor. Soc. Obes., 1:21-24, 1992; Lew E A, Ann. Intern. Med., 103:1024-1029, 1985; Kim K I et al., Korean J. Food Sci. Technol., 35:720-725, 2003).
Obesity is known to be caused by genetic factors, environmental factors resulting from Westernized eating habits, psychological factors resulting from stress, and the like, but the exact causes or mechanisms of obesity have not been clearly found.
In the past, it has been recognized that adipocytes merely act to store surplus energy of the human body in the form of triglycerides and to buffer external impact. However, in the recent years, adipocytes have been recognized as an endocrine organ that secretes adipocytokines which regulate fasting metabolism and insulin sensitivity. Specifically, adipocytokines such as adiponectin, leptin, resistin, tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6) and the like are known to play an important role in maintaining homeostasis and regulating energy metabolism (Matsuzawa, Y. et al., Ann. Ny. Acad. Sci., 892:146-154, 1999; Saltiel, A. R., Nat. Med., 7:887-888, 2001).
The goals for treating obesity can be largely classified into two. The first goal is to burn an excess amount of fat to reduce body weight, and the second goal is to improve metabolic imbalance. Currently, the treatment of obesity aims not only at reducing body weight, but also at improving metabolic abnormalities by early eliminating factors that cause cardiovascular diseases. In addition, studies have been actively conducted to inhibit obesity by controlling food intake and energy expenditure.
Hypothalamus, motor nervous, autonomic nervous and peripheral nervous systems are all involved in regulation of food intake behaviors. Particularly, the hypothalamus of the central nervous system plays an important role in the pathology of obesity. Typical factors that are secreted from the hypothalamus include neuropeptide Y, POMC/CART, melanocortin receptor, norepinephrine, serotonin, and the like. Current strategies for development of obesity therapeutic agents include reduced food intake, a reduction in caloric absorption, promotion of exothermic reactions, regulation of energy metabolism, regulation of signaling through the nervous system, and the like (Mi-Jung Park, Korean J Pediatr 48(2), 2005).
Obesity therapeutic drugs known to date are largely divided according to the mechanism of action into satiety stimulants, fat absorption inhibitors, and antipsychotic appetite suppressants. The most representative drugs for obesity treatment include Xenical™ (Roche Pharmaceuticals, Switzerland), Reductil™ (Abbott, USA), Exolise™ (Arkopharma, France) and the like, but have problems in that they cause fatty stool, intestinal gas generation, abdominal bloating, fecal incontinence and the like, and causes adverse effects such as cardiac diseases, respiratory diseases, neurological diseases and the like, and the persistence of efficacy thereof is low.
Accordingly, in order to minimize the adverse effects of artificially synthesized substances as described above, functional substances effective for weight control have been developed from natural substances. However, anti-obesity substances extracted from such natural substances have problems in that the effective concentration of components that exhibit efficacy is low and many costs are incurred because the natural substances are cultivated in farmlands or the like.